To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect,
Written in heaven - enrolled as citizens there. All who at the coming of "God the Judge of all" (which clause naturally follows) shall be found "written" in the Lamb's book of life (Revelation 21:27). Though fighting the good fight on earth, still, in your destiny and life of faith, which substantiates things hoped for, ye are already members of the heavenly citizenship. Alford wrongly restricts 'the church of the first-born written in heaven' to those militant on earth; rather, all who at the Judge's coming shall be found written in heaven (the true patent of heavenly nobility; contrast "written in the earth," Jeremiah 17:13, and Esau's profane sale of his birthright, Hebrews 12:16); believers from the beginning to the end of the world form one church, to which the Hebrews were already come. The first-born of Israel were "written" in a roll (Numbers 3:40).
The spirits or just men made perfect - at the resurrection, when the "JUDGE" shall appear, and perfect believers' bliss by uniting the glorified body with the spirit: the New Testament hope (Romans 8:20-23; 1 Thessalonians 4:16). The place of this clause after "the JUDGE OF ALL" is my objection to Alford's explanation, the souls of the just in their separate state perfected. Compare (note) Hebrews 11:39-40: those heretofore spirits, but now to be perfected by being clothed upon with the body. Still, "spirits of just men made perfect" may favour the reference to the spirits in their separate state, whose perfecting by earthly trials is completed. In no other passage are the just said to be perfected before the resurrection and the completion of the number of the elect (Revelation 6:11); therefore, 'spirits of the just' may be used to express the just whose predominant element in their perfected state shall be Spirit. So spirit is used of a man in the body under the influence of the Spirit, not the flesh (John 3:6). In the resurrection bodies of the saints the spirit shall preponderate over the animal soul (note, 1 Corinthians 15:44). Others think Christ at His ascension carried the redeemed church from the paradise of Sheol or Hades to the paradise of the third or highest heaven (Matthew 27:52-53; Romans 10:6-7; Ephesians 4:9; 1 Peter 3:18; 1 Peter 3:20).